Issue
There are no minimum current or wetting currents shown on the datasheets.
Product Line
EcoStruxure Buildings Operation
Environment
- DO-FA-12 and DO-FA-12-H
- IP-IO
- Form A, B and C relay contacts
Cause
The relay outputs are not working since the minimum or wetting current was not maintained and the contacts of the relays have filmed up giving incorrect control.
Resolution
There are several relays used across this range of controllers and to ensure good low current operation, the minimum or wetting current should be 1milliamp at 5volts or greater.
Wetting current is the minimum electric current needing to flow through a contact to break through the surface film resistance of a contact. It is typically far below the contact's nominal maximum current rating.
It should also be noted that these controllers may be monitoring third party devices through their status or fault relays. An example of this would be an IP-IO monitoring a VFD for status. The IP-IO inputs will supply 3milliamp at 24volts. To ensure good lifetime operation of this output from the VFD, ensure this is within the VFDs range of minimum or wetting current.
